The invention relates to mixtures of linear organosiloxanes, to processes for their preparation, and to a process for the preparation of cosmetic formulations.
Volatile siloxane compounds have a broad spectrum of use in a large number of areas, including in cosmetics as volatile carrier substances. Because of their low heat of evaporation, volatile siloxane compounds usually evaporate without causing a feeling of cold or burning on the skin.
Because of the high vapor pressure and the low boiling point, the volatile siloxane compounds evaporate quickly and without leaving a residue. The evaporation rate must not, however, be so great that there is insufficient time to uniformly apply, distribute, rub in, or work in the formulation containing the volatile siloxane compounds on skin, hair, etc. In addition, the treated sites should not become dried out, but should remain smooth and soft.
The siloxanes used most frequently are cyclic siloxanes having from 4 to 6 siloxane groups (commonly designated D4, D5, D6) which contain exclusively methyl groups, and in particular, mixtures thereof, since these have a favorable rate of evaporation. However, D4 is currently suspected of having a reproduction-toxic effect.
U.S. Pat. Nos. 5,002,762 and 5,084,577 describe diversely substituted linear siloxanes for use in cosmetics. Siloxane mixtures with a favorable evaporation behavior are not disclosed. The linear siloxanes in U.S. Pat. No. 5,002,762 contain, as radicals, functional groups which can undergo undesired and incalculable interactions in cosmetic formulations.
The object of the present invention is to provide volatile carrier substances suitable for use in cosmetics, which do not contain cyclic siloxanes having from 4 to 6 siloxane groups, which are very inert, and which have good compatibility with a large number of other cosmetic raw materials.
The invention provides mixtures of linear organosiloxanes of the general formula 1
R3SiOxe2x80x94(SiR2O)nxe2x80x94SiR3xe2x80x83xe2x80x83(1)
where
R can be identical or different and is a hydrocarbon radical having from 1 to 18 carbon atoms which is optionally substituted by fluorine, chlorine or cyano radicals and is free from ethylenically or acetylenically unsaturated bonds, and
n has values from 0 to 20,
where the mean number of carbon atoms of the radicals R is at most 3 and
where the mixtures have evaporated, measured in accordance with DIN 53249,
to an extent of from 80 to 95% by weight after 30 minutes,
to an extent of from 90 to 99% by weight after 60 minutes and
to an extent of from 95 to 100% by weight after 120 minutes.
The invention is based on the discovery that the mixtures of linear organosiloxanes have a considerably more favorable evaporation behavior than even the cyclic siloxanes having from 4 to 6 siloxane groups.
The rates of evaporation are measured in accordance with DIN 53249 by
1. weighing a round filter paper of diameter 150 mm,
2. applying a 0.3 ml sample using a pipette, and immediately weighing the filter and
3. weighing the filter at 5 min intervals at RT (25xc2x0 C.) in a draught-free place.
In each case amounts are weighed to an accuracy of 0.001 g.
Examples of radicals R are alkyl radicals such as the methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, and tert-pentyl radicals, hexyl radicals such as the n-hexyl radical, heptyl radicals such as the n-heptyl radical, octyl radicals such as the n-octyl radical and isooctyl radicals such as the 2,2,4-trimethylpentyl radical, nonyl radicals such as the n-nonyl radical, decyl radicals such as the n-decyl radical, dodecyl radicals such as the n-dodecyl radical, octadecyl radicals such as the n-octadecyl radical; cycloalkyl radicals such as cyclopentyl, cyclohexyl, cycloheptyl radicals and methylcyclohexyl radicals; aryl radicals such as the phenyl, naphthyl and anthryl and phenanthryl radicals; alkaryl radicals such as o-, m-, p-tolyl radicals, xylyl radicals and ethylphenyl radicals; aralkyl radicals such as the benzyl radical and the xcex1-and the xcex2-phenylethyl radicals.
Examples of substituted radicals R are cyanoalkyl radicals, such as the xcex2-cyanoethyl radical, and halogenated hydrocarbon radicals, for example halogenoalkyl radicals, such as the 3,3,3-trifluoro-n-propyl radical, the 2,2,2,2xe2x80x2, 2xe2x80x2,2xe2x80x2-hexafluoroisopropyl radical, the heptafluoroisopropyl radical, and halogenoaryl radicals, such as the o-, m-, and p-chlorophenyl radicals.
Preferably, the radical R is a linear alkyl radical, in particular having from 1 to 10, in particular from 1 to 6, carbon atoms. Particularly preferred radicals R are ethyl and, in particular, methyl radicals.
n preferably has values of at most 12, in particular at most 10.
The mean number of carbon atoms of the radicals R is preferably at most 2, in particular at most 1.5.
In a preferred embodiment in which R is a methyl radical, n in
0.5 to 20% by weight of the organosiloxanes has the value 0, in
20 to 65% by weight of the organosiloxanes has the value 1, in
10 to 40% by weight of the organosiloxanes has the value 2, in
0.5 to 20% by weight of the organosiloxanes has the value 3, in
0 to 10% by weight of the organosiloxanes has the value 4, in
0 to 5% by weight of the organosiloxanes has the value 5, and in
0 to 5% by weight of the organosiloxanes has the values 6 to 20.
In a particularly preferred embodiment in which R is a methyl radical, n in
6 to 12% by weight of the organosiloxanes has the value 0, in
45 to 55% by weight of the organosiloxanes has the value 1, in
22 to 30% by weight of the organosiloxanes has the value 2, in
6 to 12% by weight of the organosiloxanes has the value 3, in
1 to 5% by weight of the organosiloxanes has the value 4, in
0 to 3% by weight of the organosiloxanes has the value 5, and in
0 to 1% by weight of the organosiloxanes has the value 6 to 20.
Preferably, the mixtures have evaporated, measured in accordance with DIN 53249, to an extent of from 20 to 80% by weight, in particular an extent of from 30 to 70% by weight after 5 minutes, and to an extent of from 60 to 90% by weight, in particular to an extent of from 70 to 85% by weight after 15 minutes.
Preferably, the mixtures have evaporated, in accordance with DIN 53249, to an extent of from 85 to 94% by weight after 30 minutes, to an extent of from 94 to 97% by weight after 60 minutes and to an extent of from 97 to 99.5% by weight after 120 minutes.
The mixtures of linear organosiloxanes are preferably prepared by hydrolyzing a mixture of 1 part of trimethylchlorosilane and from 2.5 to 6 parts, preferably from 3.5 to 4.5 parts, of dimethyldichlorosilane in hydrochloric acid.
Preferably, in a second step, excess organosiloxanes of the general formula 1 in which n has the values from 0 to 2 are separated off, preferably by distillation. In the hydrolysis, the concentration of the hydrochloric acid is preferably kept constant by metering in water. The concentration of the hydrochloric acid is preferably from 15 to 25% by weight.
The mixtures of linear organosiloxanes are used in the preparation of cosmetic formulations. The mixtures of linear organosiloxanes are advantageously used in a variety of diverse cosmetic applications, for example in formulations from the field of haircare, such as hairspray, shampoo, mousse, styling gel, styling lotion, conditioner, hair dyes, hair bleaches, etc.; formulations from the field of antiperspirants and deodorants; formulations from the field of skincare, such as body lotion, hand creams, moisturizing creams, baby creams, etc.; formulations from the field of sun protection, such as suncreams, sun milk, lip protection, etc. and formulations from the field of covering cosmetics, such as lipstick, mascara, face powder, foundation, etc.
The mixtures of linear organosiloxanes aid the uniform distribution of active ingredients on skin and hair. In decorative cosmetics, despite rapid evaporation, they offer sufficient time for processing, and as a result improve the application properties, reduce tack and make the skin smoother and softer. In haircare applications, volatile siloxane compounds aid uniform distribution of high-viscosity oils, improve wet combability and act as resin plasticizers in hair-setting/styling products.
A large number of cosmetic formulations contain fragrances. As a result of their rapid evaporation behavior at the start, in particular up to 30 min, in accordance with DIN 53249, the mixtures of linear organosiloxanes cause the top note of the fragrance used to be evident particularly quickly and prominently. As a result of the reduced evaporation rate after 30 min in accordance with DIN 53249 and the particularly greatly reduced evaporation rate up to 60 min in accordance with DIN 53249, the base note of the fragrance is retained for a particularly long period.
The invention is illustrated in more detail by reference to the examples below. All parts and percentages are by weight. The examples are carried out at a pressure of the ambient atmosphere, i.e. at about 0.1 MPa, and at room temperature, i.e. at about 21xc2x0 C.